[What is needed to develop a headache? Anatomical and pathophysiological implications]

The shared anatomical and physiological substrate for headache syndromes is the neural innervation of the cranial circulation. Evidence suggests, that the observed dilatation of vessels in trigeminal pain is not inherent to a specific headache syndrome but rather a feature of the physiology of the trigeminal neural innervation of the cranial circulation. Moreover, the impact of vascular changes for the generation of headaches remains elusive. The trigeminal nerve innervates blood vessels within ipsilateral meninges. Upon activation neuropeptides such as CGRP are released. Blockade of both the trigeminal nerve system and neuropeptides are crucial targets for headache alleviating drugs. While these mechanisms are well known the events within and outside the CNS which initiate headaches are poorly understood. This article will review the anatomy and physiology of the trigeminovascular system which demand renewed consideration of the neural influences in many primary headaches.